The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely sophisticated devices, and computer systems may be found in many different environments. Since the dawn of the computer age, the performance of computers has been measured to determine how well the computer performs certain tasks. One measure of computer performance is reliability, availability and serviceability (RAS). Diagnostic mechanisms are often provided to increase the RAS of computer systems. In general, diagnostic mechanisms detect and analyze errors or faults that occur in the hardware and software portions of a computer system while the system is being tested or operated. A diagnostic mechanism in a computer system typically detects errors or faults as they occur and logs such errors or faults for later analysis by a diagnostic program.
For example, a power fault diagnostic mechanism in a computer system detects and analyzes faults in the power system of the computer system. The terminology “power system” is used herein to broadly define the system that applies power to various electronic components of the computer system, such as the central electronics complex (CEC), mass storage devices, etc. Detecting and analyzing faults in the power system is complicated by the interactions and false indications caused by utility power disturbances. Such disturbances occur when the input power provided to the power system, typically from a utility, falls outside of specified limits for varying amounts of time from milliseconds to hours. Utility power disturbances include total outages, often referred to as blackouts, and power reductions, often referred to as brownouts, and transient distortions.
Conventional power fault diagnostic mechanisms typically employ an alternating current (AC) loss detector to detect utility power disturbances. Nonetheless, when a utility power disturbance occurs, conventional power fault diagnostic mechanisms often give a false indication or no indication of what happened. If detected, the utility power disturbance is logged into volatile memory. Since the loss of power can be sudden and unexpected, there is typically no time to create a non-volatile record of the event once it happens. If the utility power disturbance persists long enough, the volatile record of the event is lost. Since no log of the fault remains, the conventional power fault diagnostic mechanism in this situation can provide no indication of what happened. In the false indication situation, the conventional power fault diagnostic mechanism provides a false indication that a fault occurred in the power system because the AC loss detector failed to detect a utility power disturbance. An AC loss detector may fail to detect a utility power disturbance for a variety of reasons. For example, the threshold at which the AC loss detector detects a utility power disturbance may be set relatively high to avoid false positives due to variances in the power system, its load and the AC loss detector. Likewise, the power system may be affected by a utility power disturbance that is not detected by the AC loss detector due to factors such as wave shape or harmonics, the response time of the AC loss detector, etc. Each of these situations, i.e., the no indication situation and the false indication situation, is likely to lead to an unnecessary service call and possibly to the unnecessary replacement of power system components.
U.S. Pat. No. 4,533,865 to Schlenk discloses a circuit arrangement for identifying and storing power line faults in data processing systems. A rectified power line voltage is supplied to a comparison circuit for comparison to a reference voltage. When the rectified power line voltage falls below the reference voltage, the event in recorded in a memory that comprises a bistable relay. As a result, power line faults remain stored despite the return of power line input voltage. However, the comparison scheme used by this circuit arrangement provides inconsistent results. On one hand, the circuit arrangement may identify a utility power disturbance that does not affect the power system due to variances in the power system, its load and the circuit arrangement. In other words, the circuit arrangement may indicate a utility power disturbance that the power system rides through. On the other hand, the power system may be affected by a utility power disturbance that is not identified by the circuit arrangement due to factors such as wave shape or harmonics, the response time of the circuit arrangement, etc. Moreover, the circuit arrangement employs an inhibit signal to block the memory both during run up of the rectified power line input voltage and when the overall data processing system is turned off. As with the comparison scheme, differences in thresholds may cause different, inconsistent results during the run-up inhibit. Also, employing the inhibit signal when the data processing system is turned off will prevent the circuit arrangement from recording a utility power disturbance that could have affected the system had the system been turned on. Finally, the circuit arrangement adds significant cost to the data processing system.
Therefore, there exists a need to provide an enhanced power fault diagnostic mechanism that better identifies and records utility power disturbances.